Support multiple inheritance in Contract

[gab-fin]

It would be great to support it, we have a hierarchy of interfaces and it represents a lot of work/duplication to flatten it out. I believe that this is request 3 :-).

[kdavisk6]

Please do create duplicate issues.

[gab-fin]

@kdavisk6, I created this because the other one was closed. In this case you should re-open the other one.

[velo]

@gab-fin are you volunteering to work on it?